The Torah specifies (Shemos 16:29) “Let everyone remain where he is: let no one leave his place on the seventh day”; one may not exit one’s premises on Shabbos. Does this include traveling through time, or is one free to roam the annals of history ?
A deep understanding of the Theory of Relativity is necessary for a Torah scholar - only מיוחסים (Experts in relativity) can be on the Great Sanhedrin. One of the principles of relativity is that space and time intervals are equivalent, with the conversion factor being the speed of light.
We can then see that a person may travel in time only by the equivalent of 2000 amot - which is around 3 microseconds. Unfortunately, that means that traveling through history on Shabbat is forbidden.
One of the standard Shabbat songs states in reference to the day of Shabbat:
יונה מצאה בו מנוח
On it Jonah found Manoah.
As Jonah lived after Manoah, he could only have found him via time travel. As the song states that he found him on Shabbat, this may indicate that time travel is permitted on Shabbat. Though I suppose one could argue that he time travelled prior to Shabbat and only found Manoah on Shabbat.
Note that there is external confirmation beyond the song that Manoah was indeed visited by by a prophet. Judges 13:13 states:
ויאמר מלאך ה' אל מנוח
And the angel of the Lord said to Manoah.
Ralbag in his commentary writes:
והנה זה המלאך שדבר למנוח ולאשתו היה נביא בהכרח
And this angel that spoke to Manoah must have been a prophet.
Presumably, then, Scripture is describing this very meeting of the prophet Jonah with Manoah.
On the other hand, there is some evidence that this may not have actually occurred, and Manoah would not be a trustworthy source. R. Saadia Gaon in Emunot V'Deiot writes:
Thus, for example, certain monotheists shunned the view that God was unable to bring back yesterday in order not to ascribe to him impotence. They thereby, however, let themselves into something worse by ascribing to God an absurdity, as we shall note in part of the second treatise of this book, if God, exalted be He, is willing.
(Rosenblatt translation p.25, my emphasis)
It will not, therefore, praise Him for being able to cause five to be more than ten without adding anything to the former, nor for being able to put the world through the hollow of a signet ring without making the one narrower and the other wider, nor for being able to bring back the day gone by in its original condition. For all these things are absurd.
(Rosenblatt translation p. 134, my emphasis)
From this it seems that time travel is not in fact possible, even for God, and only someone ignorant would believe that it is possible. And we know that Manoah was ignorant, as the Talmud (Berachot 61a and parallels) explicitly declares that he was an am ha'aretz:
אמר רב נחמן מנוח עם הארץ היה
R. Nachman said "Manoah was an ignoramus".
Thus, apparently Manoah would have simply been one of the ignoramuses who believed the absurdity that time travel was possible, even though in actuality it is not.
However, to make matters more complicated, if this indeed occurred on Shabbat then perhaps we should trust Manoah. As Rambam explains in his commentary to Demai 4:1
אמרו בתלמוד שהטעם בעניין שהוא נאמן בשבת לפי שאימת שבת עליו רוצה לומר שעמי הארץ הוא חמור בעיניהם לעשות עבירה ביום שבת מפני כבוד היום לפיכך לא ישקר
They said in the Talmud that the reason for the fact that he is believed on Shabbat is that the awe of Shabbat is upon him. Meaning to say that the ignoramuses (amei ha'aretz) consider it serious in their eyes to do a sin on the day of Shabbat because of the honor of the day; therefore he will not lie.
This would seem to indicate that even Manoah the am ha'aretz should be believed about the claim of time travel, as long as he claimed it on Shabbat.
However, this only seems to mean that we believe that he is not (deliberately) lying, but who is to say that he is not simply mistaken even though he believes he is telling the truth?
To address this we need to reconcile a contradiction posed by an explicit Mishnah (Avot 2:5) which says:
אין בור ירא חטא ולא עם הארץ חסיד
A boor does not fear sin, nor (even) a pious ignoramus.
This seems to be saying that an ignoramus does not fear sin even at the time when he is pious, i.e. on Shabbat when the fear of the holy day is upon him. In order to reconcile the previous explanation with this Mishnah we would have to say that when Rambam said that the ignoramus wouldn't lie, he didn't mean that he wouldn't deliberately engage in the sinful activity of telling an untruth (since we just established that even on Shabbat he does not fear sin); rather he meant that he wouldn't utter any untruth at all even mistakenly.1
If this is the case then we would have to assume that Manoah would not only be trusted to tell the truth, but he would even be trusted to provide an ignoramus's perception of the truth. We would then have to accept Manoah's account even over the philosophical objections of R. Saadia Gaon. In case the reader feels uncomfortable attributing such an error to R. Saadia Gaon, it should be noted that he himself acknowledges such a possibility in his introduction:
Although I do acknowledge that my learning is far from perfect and admit that any scientific attainments are lacking in excellence, and I am not wiser than my contemporaries,
(Rosenblatt translation p. 8)
And shortly thereafter:
I also adjure by God, the creator of the universe, any scholar who upon studying this book, sees in it a mistake, that he correct it, or, should he note an abstruse phrase, that he substitute for it a more felicitous one. Let him not feel restrained therefrom by the fact that the book is not his work, or that I had anticipated him in explaining what had not been clear to him.
(Rosenblatt translation p. 8)
So in sum, it seems that there is certainly a case that can be made for the permissibility of time travel on Shabbat, though it is not quite iron-clad.
The Sages instituted that we may not travel more than 2000 amot in any direction outside of our techum on Shabbat. This is clearly symmetric, and in Minkowski space, there is no reason to think that the Sages distinguished between space or time directions. Let us make this precise.
The Minkowski (pseudo-)metric is dw2=dx2+dy2+dz2–dt2, where x, y, and z are spatial coordinates and t is the time coordinate. Then the Sages instituted that the maximum distance outside the techum must be at most 2000 amot when measured with the associated distance function.
If we assume that the starting point is the origin, and one leaves the techum immediately upon leaving the origin, it follows that the Shabbat boundary is the sphere of radius 2000 amot in Minkowski space, given by |x2+y2+z2–t2|=20002. We cannot draw this exactly, but we can illustrate this by collapsing all the spatial dimensions onto one axis s, and graphing |s2–t2|=20002:
The locations that are permissible are the component containing the origin. As we can see, there are permissible locations that have arbitrarily large values of |t|, and it follows that time travel on Shabbat is permissible.
The problem with time travel is that while you are traveling, you acquire the status of a plant (צומח). The distinctive characteristic of a plant is that it can travel through time (at the "normal rate"), but it can't travel through space.
Therefore, by exiting the time machine, you would be performing the מלאכה of תולש, so it would be forbidden.
As long as you don't time travel to before the local eruv was erected, you should be fine.
I'm not Jewish, but it's my understanding that most Jewish communities erect a wire called an eruv around the geographical area they live in, so that it's all technically considered one house, allowing them to go out and about their neighborhood without breaking the Law about leaving their homes during the Sabbath.
As a result, if you were to time travel on the Sabbath, and you remain within the boundaries of the local eruv, both in time and space, you would be fine, because you've technically never left the house!
The space-time distance conversion is not applicable here. While attempting time travel, the distance moved as a direct result of time travel becomes 0 in proper time. Since the Almighty is everywhere, proper time is as good of reference frame as any other. However, no matter where in time you travel, it is still the sabbath for you.
Since you're intent on asking whether its permitted without saying how, I shall enumerate the ways.
Time travel by wormhole: You're outside the solar system. Since the sun has not set, the sabbath has not started. But don't leave the vicinity of Earth on the sabbath because you're not allowed to travel.
Time travel by time warp: distance traveled in proper time in a warp field is zero. Unfortunately for you, constructing the warp field is doing work. A sabbos switch will not save you.
Time travel by fixed teleporter or teleportation ring or pre-created pulled-apart anomaly: The geometry of the universe is non-simple. Measure the appointed distance through the geometry as given. If you can walk less than two thousand cubits and arrive at your house you have not traveled farther than two thousand cubits from your souse.
Time travel by opening a teleportation gate: you did work on the sabbath.
Time travel by teleport ability: after putting in the GE correction for earth's orbit, there's no way you didn't travel too far. Two thousand cubits does not go very far in accounting for Earth's precession.
Time travel by teleport ability without traveling any distance: you just spaced yourself.
This is easy.
- G-d was, is and will be, before all.
- G-d was, is and will be, after all.
- There is only one G-d
Therefore before and after are the same. And, if not in our eyes then we lack wisdom, and they are the same in the eyes of G-d.
And if before and after are the same, then time travel is no travel at all, for we travel from a place and time, to the same place and same time, and it is allowed.
See medrash rabbah in last week's parsha
דבר אחר "וְאֵלֶּה הַמִּשְׁפָּטִים" הדא היא דכתיב (תהלים קמז, יט) "מגיד דבריו ליעקב" אלו הדברות. "חוקיו ומשפטיו לישראל" אלו המשפטים. לפי שאין מדותיו של הקב"ה כמדת ב"ו מדת ב"ו מורה לאחרים לעשות והוא אינו עושה כלום הקב"ה אינו כן אלא מה שהוא עושה הוא אומר לישראל לעשות ולשמור. מעשה ברבן גמליאל ור' יהושע ור"א בן עזריה ור' עקיבא שהלכו לרומי ודרשו שם אין דרכיו של הקב"ה כבשר ודם שהוא גוזר גזירה והוא אומר לאחרים לעשות והוא אינו עושה כלום והקב"ה אינו כן. היה שם מין אחד אחר שיצאו אמר להם אין דבריכם אלא כזב לא אמרתם אלהים אומר ועושה. למה אינו משמר את השבת אמרו לו רשע שבעולם אין אדם רשאי לטלטל בתוך חצירו בשבת אמר לו הן. אמרו לו העליונים והתחתונים חצירו של הקב"ה שנאמר (ישעיה ו, ג) "מלא כל הארץ כבודו" ואפילו אדם עובר עבירה אינו מטלטל מלא קומתו אמר לו הן. אמרו לו כתיב (ירמיה כג, כד) "הלא את השמים ואת הארץ אני מלא".
So if Hashem is allowed to carry on Shabbos because the universe is His reshus then He can also time travel on Shabbos, because the whole of history is His reshus also.
But what about us?
This depends on your madregah.
If you are on the madregah of Noach who walked with Hashem, then it is mutar, because relatively you never leave Hashem, so you haven't moved and are still in the same reshus.
Whereas, if you are on the madregah of Avraham
וַיְהִי אַבְרָם בֶּן תִּשְׁעִים שָׁנָה וְתֵשַׁע שָׁנִים וַיֵּרָא יְהוָה אֶל אַבְרָם וַיֹּאמֶר אֵלָיו אֲנִי אֵל שַׁדַּי הִתְהַלֵּךְ לְפָנַי וֶהְיֵה תָמִים.
Then saying that the entire history is one reshus does not help you because you went before Hashem, so you are now in a new reshus and it is assur.
I have an answer but, sadly, cannot find the gemara where it comes from.
There is a machloket whether a kupat tzedach can borrow money in order to give to poor people. The, when more money comes in, they repay the debt.
The "nay" opinion say that since the money, when given by the donator, does not go to tzedach it means that the donator is not keeping his neder of giving. The "yea" opinion says that "G-d exists everywhere all the time".
According to this, I would say that this is the same machloket.
If G-d is everywhere all the time, then there should be no problem.
I will try to find the sources and add them.
The verse is clear that one must remain in his place. Generally speaking, one's place is the house they are staying in. So one can only time travel if they will remain in their house. So you cannot travel to before the house was built. And likewise, you can only travel in the future if you know for sure your house will still be standing, because safek d'oraisa lechumrah.
If you live inside an eruv, then your place extends to the entire eruv. You can time travel anywhere within the eruv after it was built. You cannot travel to the future because who says the eruv will be up that week. Maybe there was a storm the day before, so it was down for that Shabbos until they fixed it later. Unless you time traveled during the week to make sure the eruv was up the entire time.
(There are those who ask why the same concern does not apply to a house. These people are annoying.)
If you live in a city that is entirely surrounded by an eruv, you should theoretically be able to time travel anywhere in the city if you rely on the eruv. Personally, I don't rely on the eruv, and I am embarrassed to know you. The Rabbanim of the future will definitely say the eruv is passul, you'll see.